Superb start to a long-awaited application!
(Is there a 'tip jar' anywhere?)
I think I understand the basic functionality between CollectionsManager and Calibre (via PlugIn), in that the updating process is only 1-way... I can manage the collections from Calibre and then update the Kindle -- that works great.
I don't see, however, a method for updating Calibre with any changes made on the Kindle (through native CollMgr or your utility). Importing Collections into Calibre doesn't see any Collections that were created/assigned on the Kindle.
Perhaps your menu could include an option to prepare/update the file that will be used by the Calibre plug-in as the source for imports?
I think that would result in a functional bi-directional support!
Thanks for this tremendous utility!